#import "FrtcAESObject.h"
#import <CommonCrypto/CommonCryptor.h>

static FrtcAESObject *sharedAECObject = nil;

@implementation FrtcAESObject

+ (FrtcAESObject *)sharedAESObject {
    @synchronized(self) {
        if (sharedAECObject == nil) {
            sharedAECObject = [[FrtcAESObject alloc] init];
        }
    }
    return sharedAECObject;
}

-(NSData*)AES256EncryptWithKey:(NSString *)key withData:(NSData *)data {

     // 'key' should be 32 bytes for AES256, will be null-padded otherwise
    char keyPtr[kCCKeySizeAES256 + 1]; // room for terminator (unused)
    bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)

 // fetch key data
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];

    NSUInteger dataLength = [data length];

     //See the doc: For block ciphers, the output size will always be less than or
 //equal to the input size plus the size of one block.
 //That's why we need to add the size of one block here
     size_t bufferSize           = dataLength + kCCBlockSizeAES128;
    void* buffer                = malloc(bufferSize);

    size_t numBytesEncrypted    = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES,  kCCOptionPKCS7Padding| kCCOptionECBMode,
                                           keyPtr, kCCKeySizeAES256,
                                           NULL /* initialization vector (optional) */,
                                           [data bytes], dataLength, /* input */
                                           buffer, bufferSize, /* output */
                                           &numBytesEncrypted);

    if (cryptStatus == kCCSuccess) {
        //the returned NSData takes ownership of the buffer and will free it on deallocation
        return [NSMutableData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
    }

    free(buffer); //free the buffer;
    
    return nil;
 }

 - (NSData*)AES256DecryptWithKey:(NSString*)key withData:(NSData *)data {
     // 'key' should be 32 bytes for AES256, will be null-padded otherwise
     char keyPtr[kCCKeySizeAES256 + 1]; // room for terminator (unused)
     bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)

 // fetch key data
     [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];

     NSUInteger dataLength = [data length];

     //See the doc: For block ciphers, the output size will always be less than or
 //equal to the input size plus the size of one block.
 //That's why we need to add the size of one block here
     size_t bufferSize           = dataLength + kCCBlockSizeAES128;
     void* buffer                = malloc(bufferSize);

     size_t numBytesDecrypted    = 0;
     CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES, kCCOptionPKCS7Padding| kCCOptionECBMode,
                                           keyPtr, kCCKeySizeAES256,
                                           NULL /* initialization vector (optional) */,
                                           [data bytes], dataLength, /* input */
                                           buffer, bufferSize, /* output */
                                           &numBytesDecrypted);

     if (cryptStatus == kCCSuccess) {
         //the returned NSData takes ownership of the buffer and will free it on deallocation
         return [NSMutableData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
     }

     free(buffer); //free the buffer;
     
     return nil;
 }

@end
